The present invention is directed to a communications interface apparatus adaptable for use with an analog-digital-analog conversion device for effecting communications between an analog device and a digital device. Specifically, in its preferred embodiment, the present invention is used in effecting communications between a voice-band device, such as a telephone, and a data processing device.
The present invention receives digital signals from an analog-digital-analog conversion device, decimates those incoming digital signals to produce decimated incoming digital signals representative of the received incoming digital signals. The decimated incoming digital signals are recognizable by the data processing device.
The present invention also receives outgoing digital signals from the data processing device, interpolates those outgoing digital signals to produce an interpolated digital signal which is converted to an outgoing analog signal representative of the outgoing digital signal by an analog-digital-analog conversion device. The outgoing analog signal is recognizable by the analog device.
In the manufacturing of devices such as the present invention, it is common that separate duplicate components be utilized for the decimation of incoming digital signals and for the interpolation of outgoing digital signals. Often there is duplication of components between the decimation circuitry and the interpolation circuitry.
Such use of duplicate components results in several disadvantages. For example, in integrated circuit embodiments, the cost increase occasioned by such component duplication is not significant. However, such duplicate components require additional trimming during manufacture in order that gains, accuracy, and offsets and biases are balanced within the device.
Another disadvantage is that the use of duplicate components necessarily requires that a greater chip area be occupied. Thus, the smallness of a chip implementation of such a device is inherently limited by the necessity to duplicate components to effect the two functions required, decimation and interpolation.
The present invention is designed to overcome some of the shortcomings of duplicate-component interface apparata.